minor symfony#20639 [Cache] Mark FilesystemAdapterTrait as internal (nicolas-grekas)

This PR was merged into the 3.2 branch.

Discussion
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[Cache] Mark FilesystemAdapterTrait as internal

| Q             | A
| ------------- | ---
| Branch?       | 3.2
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Commits
-------

62a1958 [Cache] Mark FilesystemAdapterTrait as internal

Author: nicolas-grekas

src/Symfony/Component/Cache/Adapter/FilesystemAdapterTrait.php

@@ -15,6 +15,8 @@
 
 /**
  * @author Nicolas Grekas <p@tchwork.com>
+ *
+ * @internal
  */
 trait FilesystemAdapterTrait
 {

src/Symfony/Component/Cache/Tests/Adapter/AdapterTestCase.php

@@ -28,8 +28,6 @@ public function testDefaultLifeTime()
     {
         if (isset($this->skippedTests[__FUNCTION__])) {
             $this->markTestSkipped($this->skippedTests[__FUNCTION__]);
-
-            return;
         }
 
         $cache = $this->createCachePool(2);
@@ -51,8 +49,6 @@ public function testNotUnserializable()
     {
         if (isset($this->skippedTests[__FUNCTION__])) {
             $this->markTestSkipped($this->skippedTests[__FUNCTION__]);
-
-            return;
         }
 
         $cache = $this->createCachePool();